Blower



v July'zs, 1942.

F. G. MARBACH BLOWER v Filed April 1o, 1941 3 Sheets-Sheer:I 1

INVENTOR.

ATTORNEYS i4 if F76, 42

July 28, 1942.

F. G. MARBACH BLOWER Filed April 10, 1941 3 Sheets-Sheet 2 INVENTOR.n/VK 6. /VZ/eanc/-f ATTORNEYS July 2s, `1942. G, MARBACH 2,291,480

BLOWER Filed April 10, 1941 5 Sheets-Sheet 3 1N VENTOR. FPA/vr 6.Mea/4c# 14@ mm gfwg ATTORNEY .5'

Patented July 28, 1942 BLOWER Frank G. Marbach, Cleveland, Ohio,assignor to Morrison Products, Inc., Cleveland, Ohio, a corporation ofOhio Application April 10, 1941, Serial No. 387,931

12 Claims.

This invention has to do with the manufacture of blowers, and relatesmore particularly to an improved sheet metal construction forcentrifugal blower Wheels. This application is, in part, a continuationof my original application, Serial No. 258,009, filed February 23, 1939,now Patent No. 2,242,586, granted May 20, 1941. Certain methodoperations herein disclosed, but not claimed, are claimed in copendingapplication Serial No. 419,605, led November 18, 1941.

An object of my invention is to provide an improved construction forblower wheels in which sheet metal can be used for all of the parts thusenabling the blower wheel to'be economically manufactured through theuse of stamping operations.

Another object of my invention is to provide an improved blower Wheel,of the centrifugal type, having an annular series of elongated bladesand embodying ring structures or spiders stamped from sheet metal andconnected to the ends of the annulus to impart strength and stiffnessthereto and to also form axially spaced mounting means by which theblower wheel may be mounted on a shaft.

A further object of my invention is to provide an improved constructionfor centrifugal blower wheels in which a strip of sheet metal having aseries of blades formed thereon is rolled into an annulus and a pair ofspiders constructed from sheet metal and having rims of channel-shapedcross-section are connected with the annulus with the ends of the latterextending into the channel recess of the rims.

Still another object of my invention is to provide an improvedconstruction for blower wheels in which an annular series of bladesformed from a strip of sheet metal remain connected at their ends byportions of such strip which provide flanges on the annulus, and inwhich such flanges have gathers therein for decreasing the spacing ofthe blades and flat portions alternating with the gathers by whichspiders can be connected with the ends of the annulus.

My invention may be further briefly summarized as consisting in certainnovel combinations and arrangements of parts hereinafter described andparticularly set out in the appended claims.

In the accompanying sheets of drawings,

Fig. 1 is a perspective view, with portions broken away, showing acentrifugal blower wheel embodying my improved construction;

Fig. 2 is a partial transverse sectional view of the blower wheel takenas indicated by line 2 2 of Fig. 1;

Figs. 3 to 6, inclusive, are partial perspective views showingprogressive steps used in forming a series of blades from a strip ofsheet metal;

Figs. '7 to 9, inclusive, are partial transverse sectional views takenthrough the blade strips of Figs. 4, 5 and 6, respectively, as indicatedby the section lines 1 1, 8-8 and 9-9 thereof.

Fig. 10 is a partial side elevation showing a modified construction formy centrifugal blower Wheel;

Fig. 11 is a partial transverse sectional view taken through suchmodified blower wheel as indicated by section line ll-Il of Fig. 10;

Fig. 12 is a partial side elevation of a blower wheel generally similarto that of Fig. 1 but illustrating a modified construction;

Fig. 13 is a partial transverse sectional View taken through thismodified blower wheel as indicated by line I3-l3 of Fig. 12.

Fig. 14 is a plan View showing a sheet metal strip used in producing themodified construction of Figs. 12 and 13;

Fig. 15 is an edge View of the strip; and

Fig. 16 is a partial plan view showing another sheet metal strip whichmay be used in producing a blower wheel of the modified construction ofFigs. 12 and 13.

Further reference will now be made to the accompanying drawings in whichI have illustrated my improved construction for centrifugal blowerwheels and although the different embodiments are described inconsiderable detail, it will be understood, of course, that the drawingsare intended to be illustrative and that the invention is not to beregarded as limited to the particular blower wheels and details ofconstruction herein disclosed.

In Fig. 1 I show a centrifugal blower wheel I5 which, according to myimproved construction, is formed entirely of sheet metal. The blowerwheel here shown comprises an annulus or cylinder I6 formed of a seriesof elongated substantially parallel transversely curved sheet metalblades Il, and a pair of ring structures or spiders I8 and I9 connectedwith the ends of the annulus and serving both as a stiffening means anda means for mounting the blower wheel on a shaft. As will be explainedmore in detail hereinafter, the blades I1 are all formed from a singlestrip of sheet metal by stamping operations performed thereon so as toleave the blades connected with each other along edges of the strip.These connecting edge portions of the strip are crimped or corrugatedfor the purpose of gathering the metal and thereby reducing the spacingof the blades so that an increased number of blades can be accommodatedin a given circumference. The strip containing the blades is rolled orformed into the annulus IS with the corrugated portions of the stripforming end flanges or rings 20 at the ends of the annulus. These angesor rings maintain the blades in the desired circumferentially spacedrelation and provide a means by which the ends of the annulus can bereadily connected with the spiders I8 and I9, as by spot welding orother suitable connecting means, with the blades accurately conformingto the desired cylindrical or annular shape so that very little laborneed be performed on the blades after assembly for truing orstraightening the same.

The spiders I8 and I9 are formed from sheet metal by appropriatestamping operations and, as shown in the drawings, each spider comprisesa rim 22 of channel-like cross-section and a shaft-receiving hub 23connected with the rim by a plurality of radial arms or spokes 24. Byconstructing the rim 22 of channel-like crossseotion it will be seenthat a spider of strong and rigid characteristics Will be obtained andthe connection of the spider with the annulus will be facilitatedbecause an end of the annulus can be inserted into the channel recessand in so doing one or both of the axial flanges 25 and 26 of the spidermay be used as a guide means for locating the blades of the annulus inthe desired accurate cylindrical arrangement.

In Fig. 1 I show the annulus I6 formed with the integral flanges thereofextending outwardly or radially at substantially right-angles to theaxis of the blower wheel. With these flanges arranged in this manner itwill be seen that they will engage or seat against the end walls f thehollow spider rims and can be connected thereto at spaced points by thespot welding 21 or other suitable connecting means. It is not necessary,however, that these flanges of the annulus be radially extending flangesbecause they can extend axially of the blower wheel and can be connectedwith one of the anges 25 or 26 of the spider rim, preferably the formerflange, as described more in detail hereinafter and as shown in themodied construction of Figs. and 11.

The arms 2l! of the spiders are formed integral with the rims thereofand with the intermediate disk portions 29 of the hubs 23. These armsare bevelled or inclined, as shown in Fig. 1, so that they will act as adeecti'ng means during rotation of the blower wheel and will facilitatethe ow 0f air into the interior of the blower wheel instead of retardingsuch flow as they would do if they were flat arms. It will be noted fromFig. 1 that the spiders I8 and I9 are of right and left-handconstruction so that for a given direction of blower rotation the armsof both spiders will act to cause a ow of air into the blower wheelthrough the open ends thereof. It will also be noted that the spidersare connected with the ends of the annulus I6 so that the arms of onespider will be in staggered relation with the arms of the other spider.lIhis arrangement is desirable for securing a more accurate balance andin securing maximum stiiness and rigidity of the blower wheel. Whenthese spiders are connected with the ends of the annulus, as aboveexplained and as shown in Fig. 1, it will be observed that the anges and26 of the spider rims extend axially inwardly toward each other so thatthese rims form end rings which are smooth and regular in shape.

The hubs 23 are also of sheet metal construction, and in addition to theintermediate disk portion 29, include oppositely dished disk members 33and 3l secured against opposite sides of such intermediate disk portion.Each hub is provided with a shaft-receiving opening 32 and with athreaded opening 36 adapted to receive a set screw or the like. Thesehubs are more fully disclosed and claimed in my oopending application,Serial No. 382,222, filed March 7, 1941.

With the hub and spider construction above described, it will be seenthat the ends of the blower wheel can be mounted on or connected with ashaft at axially spaced points corresponding substantially with thetransverse end planes of the blower wheel and, when thus mounted, theblower wheel will not be subject to warping or twisting nor does anypart of the blower wheel project in a free over-hanging relation tobecome distorted or to produce vibrations. Moreover, it will be seenthat the construction and arrangement which I have provided for thespiders will result in the blower wheel having suicient stiffness andrigidity to prevent the same from being distorted or losing its accurateshape during shipping or handling.

My improved blower construction can be better explained by referring toFigs. 3 to 6, inclusive, which show progressive steps in the forming ofthe annulus I 6 from a Strip of sheet metal. Fig. 3 shows a strip III]of sheet metal of appropriate length such that a full set of blades fora blower wheel can be formed thereon and the strip then rolled or shapedinto an annulus to bring the blades into their desired cylindricalarrangement. Rows of openings 4I are punched in the strip adjacent theside edges thereof and the strip is slit transversely at longitudinallyspaced points by cuts 42 extending from one row of openings to theother. The cuts l2 and portions of the openings 4I thus divide the striplongitudinally into a series of elongated substantially parallelsections 43 for the subsequent formation of the blades. As, shown inFig. 3 the ends of the sections 43 remain connected with ,l thelongitudinal edge portions 43a. of the strip by means of stems 43a.which are of reduced width, that is to say, are narrower than thesections themselves.

The strip resulting from the punching and slitting just explained aboveis subjected to a forming operation in which the sections 43 are bowedor curved transversely thereof and thus formed or partially formed intoblades I'I. In so shaping the blade sections 43, the edge I 1a. of eachsection is lifted up with respect to the plane of the strip, as shown inFig. 7, so that during the subsequent metal gathering operation thisuplifted edge can shift into overlying relation to the contiguous edgeI'I'b of the adjacent section, as shown in Fig. 8. The blades I'I arelater subjected to a rocking movement about their respectivelongitudinal center lines or axes by which the blades are set at adesired angle by a twisting of the stem portion 43o while the bladesremain connected with the edge portions 40a of the strip.

The strip 4B is subjected to a forming operation in which the metal ofthe edge portions 49a is gathered at spaced points for the purpose ofreducing the spacing of the blades so that an increased number of bladescan be accommodated in a given circumference. The gathering of the metalmay be accomplished by suitably crimping or corrugating the edgeportions 43a of the strip, as shown in Fig. 7, the gathers preferablybeing for-med between the pairs of adjacent blades and at pointsopposite the punched openings 4I. By comparing the strips shown in Figs.4 and 5 of the drawings it will be seen that in gathering the metal ofthe edge portions 40al the bar-like sections 44 which are coextensivewith the punched openings 4| are pressed or drawn in a direction atright angles to the plane of the strip to form a series of corrugationsor gathers 46 which are connected with each other by the stems 43a.

For the purpose of stiifening the strip and providing a construction atthe ends of the annulus which will facilitate the attachment of thespiders I8 and I9 I may subject the strip to a fianging operation. Thisflanging of theA strip may be done either -before or after the metalgathering operation. Fig. shows the condition of the strip when thegathering is done before the anging, while Figs. 14 and 15 show thestrip iianged prior to the gathering as will be explained hereinafter.When the flanging is done after the gathering operation the corrugatededge portions 40a (Fig. 5) are bent over to a position extendingsubstantially at right angles to the plane of the strip, as shown inFig. 6, to thereby form the corrugated end flanges 48. This operationmay be performed with suitable dies and can be readily carried out bythe bending of the metal of the stems 43a on or adjacent the line atwhich these stems connect with the edge portions 40a..

The strip is rolled or shaped into an annulus or cylinder by curving thestrip substantially uniformly therealong to bring the ends into adjacentor meeting relation, during which. the integral flanges 48 are for-medinto the end rings or flanges 20 which extend outwardly generallyradially with respect to the rotation axis of the blower wheel. Theannulus thus formed is now ready for assembly with the spiders I3 and E9and this is accomplished by inserting the ends of the annulus into thechannel recesses of the rims and `connecting the flanges or end rings 20with the bottom walls of the latter. As mentioned above, this `may beaccomplishedI by spot welding 2l or any other suitable connecting means.

When the ends of the annulus are inserted into the rims of the spiders Iflnd it desirable to use one of the iianges of the spider rim, forexample the outer flange 25 thereof, as a guide means or abutment forlocating the blades and truing the annulus to cylindrical shape. Sincethe spiders themselves are accurately formed in metal working dies theflanges of their rims will be truly circular in form and hence if theouter edge of the ring or radial flange 2i) is heldl firmly against theange 25 while the annulus is being welded or otherwise connected to therim, it will be seen that the annulus will have the desired cylindricalshape after assembly and very little additional lwork will be requiredfor straightening or truing the blades. In forming the corrugations 46for gathering the metal o-f the edge portions 46a of the strip, it maybedesirable to form the corrugations of square or nearly square shape sothat the end flanges 48, and the end rings 26 resulting therefrom, willhave a series of at or nearly flat faces thereon.

These at faces provide Contact areas which will ,6I between the pairs ofadjacent blades.

be subjected to a fianging operation and if desirable the annulus may beformed with straight instead of anged ends, as mentioned above and lasshown in the modified construction in Figs. 10 and 11. In this modiedconstruction the strip is rolled into an annulus, without the formationof the radial end iianges, and the spiders are then connected with theends of the annulus. In Fig. 10 I show an annulus IGa which has beenformed in this manner and show the corrugated axially extending end ring52 of the annulus inserted into the channel recess of the rim of thespider I9a with its nat-topped corrugations or gathers 52a Iplacedagainst the inner face of the outer flange 53 of the spider andconnected therewith by spot welding or other suitable connecting means.

In Figs. 12 and 13 I have illustrated another modification of myimproved blower wheel conN struction in which a relatively strongerconnection is obtained between the ends of the blades and the end angesof the annulus and in which the gathers or corrugations are locatedcloser to the stems of the blades so as not to interfere with the spotwelding operation. Although Figs. 12 and 13 show only portions of ablower wheel, it will be understood, of course, that these viewsillustrate a construction intended to be embodied in a blower wheel ofthe same general type as that illustrated in Fig. 1.

In this modied construction the blower wheel also comprises an annularseries of transversely curved blades 6U which are connected at theirends by substantially radially outwardly extending corrugated anges 6Iformed from the same strip of sheet metal as that from which the bladesare formed, and sheet metal spiders 62 connected to such end flanges.The blades 60 are connected with the end flanges 6I by means of stems 63of reduced width which have been twisted so that the blades will havethe desired position or set in the annulus. The connections between thestems 63 and the end flanges 6I in-V clude generally triangular webs 64of metal which extend in angularly inclined or obtuse relation to theseflanges. As will be seen from Figs. 12 and 13 these webs are integrallyconnected along one side with the anges 6I and at their ends areintegrally connected respectively with the stems 63 and the corrugationsor gathers 65. These webs 64 serve to reinforce and strengthen theblades 6l) at the point of connection of the same with the end flanges6| and tend to hold the blades against deflection from their propershape and position in the annulus.

In order to obtain an increased number of blades in an annulus of agiven diameter, I form the gathers or corrugations 65 in the end flangesAs shown in Figs. l2 and 13 the gathers 65 may be formed in the endiianges 6l so as to extend axially inwardly of the annulus at pointsclosely adjacent to the stems 63 so as to leave flats Gla of relativelylarge area on the end flanges BI between the adjacent gathers. Inconnecting the annulus to the spiders 62 the ats 61a are secured againstthe inner faces of the bottom walls 66 of the spiders by suitableconnecting means, such as the spot welding indicated at 61. It will beobserved that when the gathers 65 are formed in the end flanges 6| so asto lie closely adjacent to the stems 63, the flats 61a will lie oppositethe spaces between adjacent blades thus affording clearance space whichfacilitates the spot welding indicated at 61.

In Figs. 14 and 15 I have illustrated the manner in which the bladedannulus is produced for the modied blower wheel construction of Figs. 12and 13. In these views I show a strip of sheet metal 69 on whichmetal-Working operations are performed to transform the same into astrip of transversely curved blades 60 which are integrally connected attheir ends by the corrugated flanges 6l. The strip may be advanced orfed by a step-by-step movement between suitable dies (not shown) whichare made to close on the strip between the successive advance movementsthereof to simultaneously perform a plurality of metal-workingoperations on the strip. During the advance movement of the stripbetween the successive die-closings, edge portions of the strip aredeflected or bent upwardly by suitable die means to form thelongitudinal anges 6l 'Ihe operations performed simultaneously on thestrip by the closing of the dies consist in a. punching step, a slittingstep, a blade forming or shaping step and corrugating or gathering themetal of the flanges 6|.

The punching step or operation consists in forming rows of openings 'llladjacent opposite edges of the strip. One pair of such openings isformed in the strip at each closing of the dies. These openings may beof a modified rectangular shape as shown in Fig. 14. The slitting of thestrip consists in forming transverse cuts 1I therein which extend fromthe openings of one row to those of the other row. One such transversecut or slit is formed in the strip at each closing of the dies. Theslits 'll divide the strip into contiguous sections 12, from which theblades 60 are formed, and which sections remain connected at their endswith the edge portions 'I3 of the strip by the stems 63. The forming ofthe blades consists in curving the sections transversely to produce thepartially formed blades 12a and then further forming the sections intothe blades 6D by rotating the partially formed blades '12a to a more orless upright position relative to the plane of the strip. Such rotatingof the blades may be done by twisting the stem portions 63. During eachclosing of the dies one of the sections 12 is curved into a partiallyformed blade 12a and one of the partially formed blades is furtherformed into one of the blades Si). The corrugating or gathering of theflanges 6I consists in deecting portions of these flanges at pointsYbetween adjacent blades to thereby form the gathers or corrugations 65which extend toward each other, that is, in the direction of the lengthof the blades. The forming of the gathers 65 reduces the spacing of theadjacent blades 60. One pair of such gathers is formed in the flanges 6Iduring each closing of the dies.

It will thus be seen from the manner of carrying out these metal-workingoperations, as above explained, each closing and opening of the dieswill account for the forming of one complete blade on the strip with itsadjacent pair of gathers.

In Fig. 16 I show a sheet metal strip 'l5 on which blades may be formedin the manner above explained in connection with the strips le or 69 butin which the openings 16 punched ad jacent opposite edges of the stripare substantially of the form of a rhombus. For the construction ofcertain blower wheels it may be desirable to punch openings of thisshape rather than the rectangular openings 44 shown in Fig. 3 or thespecially shaped openings 'l0 shown in Fig. 14.

From the foregoing description and the accompanying drawings it will nowbe readily seen that I have provided an improved construction forcentrifugal blower wheels by which sturdy and accurate blower wheels ofthis type can be economically produced from sheet metal. With myimproved construction and method I can produce a blower wheel having a,rigidity comparable to that of a byower wheel of the presentday type ofconstruction but which is 25% to 50% lighter in weight. This isimportant from the standpoint of economy of material and economy ofpower where the blower is operated with frequent starting and stopping.It will be seen furthermore that in accordance with my improvedconstruction a blower can be formed with a set or series of bladesstamped from a single strip of sheet metal and that sheet metal spidersattached to the ends of the annulus give the blower a desired rigidityand also provide for mounting the blower on a shaft without the use of acenter plate and without having overhanging portions of the blower whichare usually subject to distortion and frequently cause objectionablevibrations. the ends of the blades, as provided in my invention,decreases the spacing of the blades and results in a construction inwhich a larger number of blades can be accommodated in an annulus of agiven diameter. By reason of this feature a blower wheel of my improvedconstruction may embody an aggregate blade area which is 25% to 50%greater than the area of a plain cylinder having the same length andoutside diameter.

While I have illustrated and described my improved blower constructionin a somewhat detailed manner, it will be understood, of course, that Ido not wish to be limited to the details of construction hereindisclosed, but regard my invention as including such changes andmodifications as do not constitute a departure from the spirit of theinvention and the scope of the appended claims.

Having thus described my invention, I claim:

l. In a centrifugal blower wheel, a cylindrical arrangement of elongatedsubstantially parallel sheet metal blades connected at their ends byintegral generally radial flanges constituting portions of the samesheet metal body as that from which said blades are formed, said flangeshaving gathers therein between adjacent blades and the aggregate area ofthe blades of the wheel being greater than the area of a cylinder havingsubstantially the same length and outside diameter as said wheel.

2. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades having integral stemportions connecting the ends thereof with outwardly extending generallyradial anges constituting portions of the same sheet metal body as thatfrom which said blades are formed, said stem portions having twiststherein holding said blades in a substantially radial position.

3. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral generally radial ilanges constituting portions of thesame sheet metal body as that from which said blades are formed, saidflanges having gathers therein between adjacent blades and the aggregatearea of the blades of the wheel being greater than the area of acylinder having substantially the same The gathering of the metal at Ylength and outside diameter as said wheel, the ends of the blades beingconnected with said flanges by integral stems having twists thereinholding the blades in a substantially radially position.

4. In a centrifugal blower wheel, a cylindrical arrangement of elongatedsubstantially parallel sheet metal blades connected at their ends bylintegral generally radial flanges constituting portions of the samesheet metal body as that from which said blades are formed, said flangeshaving gathers therein between adjacent blades and substantially flatportions between the gathers, the aggregate area of the blades of thewheel being greater than the area of a cylinder having substantially thesame length and outside diameter as said wheel, and a pair of spidershaving shaft-receiving hubs and also having rims against which said ilatportions are secured.

5. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral generally radial flanges constituting portions of thesame sheet metal body as that from which said blades are formed, saidilanges having gathers therein between adjacent blades and havingsubstantially flat portions between the gathers, the aggregate area ofthe blades of the wheel being greater than the area of a cylinder havingsubstantially the same length and outside diameter as said wheel, theends ofthe blades being connected with said at portions by stems whichinclude an inte'gral generally triangular reinforcing web portionextending angularly to the corresponding ilat flange portion.

6. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral generally radial flanges constituting portions of thesame sheet metal body as that from which said blades are formed, saidilanges having corrugations therein between adjacent blades and havingsubstantially ilat portions between the corrugations, the aggregate areaof the blades of the wheel being greater than the area of a cylinderhaving substantially the same length and outside diameter as said wheel,and a pair of sheet metal spiders having shaft-receiving hubs andchannel-shaped rims, said flanges being secured in said channel-shapedrims with the ilat portions of the flanges seating against the bottomsof the rim recesses.

7. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral flanges constituting portions of the same sheet metalbody as that from which said blades are formed, said integral ilangesextending outwardly with respect to the rotation axis and havingalternate gathers and ilats thereon, and a pair of sheet metal spidersat the ends of the blade arrangement, said spiders havingshaft-receiving hubs and also having rims provided at their outerperiphery with axial flanges extending toward each other, the flats ofsaid integral flanges being secured against said rims with the outeredges of said integral flanges substantially in abutting relation tosaid axial flanges.

8. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral flanges constituting portions of the same sheet metalbody as that from which said blades are formed, said integral flangeshaving substantially flat-topped corrugations therein between adjacentblades, and a pair of sheet metal spiders at the ends of the bladearrangement and having rims provided with axial flanges extending towardeach other, said flat-topped corrugations being secured against theinner faces of said axial flanges.

9. In a centrifugal blower wheel, a cylindrical arrangement of elongatedsubstantially parallel sheet metal blades connected at their ends byintegral generally radial flanges constituting portions of the samesheet metal body as that from which said blades are formed, said flangeshaving offset portions between the pairs of adjacent blades and whichextend inwardly toward each other in the general direction of theblades, the aggregate area of the blades of the wheel being greater thanthe area of a cylinder having substantially the same length and outsidediameter as said wheel.

10. A centrifugal blower wheel comprising a cylindrical arrangementV ofelongated substantially parallel sheet metal blades connected at theirends by integral generally radial flanges constituting portions of thesame sheet metal body as that from which said blades are formed, saidflanges having substantially axially extending inwardly tapered offsetportions between the pairs of adjacent blades and substantially llatportions between the pairs of adjacent offset portions, the aggregatearea of the blades of the wheel being greater than the area of acylinder having substantially the same length and outside diameter assaid wheel, and a pair of spiders having shaft-receiving hubs and alsohaving rims against which said substantially flat portions of theflanges are secured.

11. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral generally radial flanges constituting portions of thesame sheet metal body as that from which said blades are formed, saidflanges having substantially axially extending inwardly tapered offsetportions between the pairs of adjacent blades and substantially flatportions between the pairs of adjacent offset portions, the aggregatearea of the blades of the wheel being greater than the area of acylinder having substantially the same length and outside diameter assaid wheel, and a pair of spiders having shaft-receiving hubs and alsohaving rims against which said substantially flat portions of theflanges are secured, said blades having stem portions of reduced widthat their ends by which they are connected with said substantially flatparts of said flanges and said stem portions being of a shape to holdsaid blades in a substantially radial position.

12. A centrifugal blower wheel comprising a cylindrical arrangement ofelongated substantially parallel sheet metal blades connected at theirends by integral generally radial flanges constituting portions of thesame sheet metal body as that from which said blades are formed, saidflanges having substantially axially extending inwardly tapered offsetportions between the pairs of adjacent blades and substantially flatportions between the pairs of adjacent offset portions, the aggregatearea of the blades of the wheel being greater than the area of acylinder having substantially the same length and outside diameter assaid wheel, said blades having stem portions of reduced Width at theirends by which they are connected with said flanges and which stemportions are of a shape to hold said blades in a substantially radialposition, and a pair of spiders having shaft-receiving hubs and alsohaving rims against which said substantially at portions of the flangesare secured by Welds, said offset portions being located relativelyclose to said stem portions and said flat portions being located to spanthe spaces between the pairs of adjacent blades so as to facilitate 5the forming of said Welds.

FRANK G. MARBACH.

